To gain insight into the mechanism of gene control, I propose to study the nature of the heat shock response in the year, Sacchoromyces cerevisiae. The response of organisms to heat and other stresses is universal and the proteins induced by treatment appear to have been conserved throughout evolution. We will study the regulation of transcription and the function of the genes in yeast related to the heat shock genes of Drosophila and other genes whose transcription is enhanced by stress. We have found a family of genes related to the major heat shock inducible genes of Drosophila melanogaster, the hsp 70 genes. A second group of genes of yeast is related to the family of heat shock genes of Drosophila present at cytological locus 67B. The approach to study the regulation and function of these multigene families as well as other stress inducible genes will be two-fold. I shall seek to determine what DNA sequences are responsible for the differential heat or stress sensitivity of these genes. The functionality of promoter regions altered in vitro using recombinant DNA techniques will be assayed in vitro utilizing a yeast transformation system. Also, mutants with altered expression of heat shock genes will be isolated and characterized. Secondly, insight into the function of the heat shock and heat shock related genes will be gained by determining the effect of deletion of functional genes and by characterization of mutants altered in these genes.